I have a vibration that feels like a wheel off balance, but only when pulling and between 100km/hr and 120km/hr (60mph and 75mph) on level road very smooth, uphill heavy vibration. No sign of the vibration below 100 or above 120... also smooths out when cornering either way!
I have swapped wheels, checked all ball joints, wheel bearings, rubbers.

Have you considered checking or getting it checked out to be sure that the engine was dropped properly and that all of the parts to keep it in place were installed correctly?

This reminds me of a problem I've had when the boots around the wheel joints in the front end start to go on my car. I'm not sure if those are the exact terms for the parts.

In that case, I've had a clicking sound when turning.